Download or read book Spectroscopic and Reactivity Studies of Binuclear Non heme Iron Complexes written by Subhasish Mukerjee and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic and Reactivity Studies of Mononuclear and Binuclear Non heme Iron Complexes written by Bala Sundari T. Kasibhatla and published by . This book was released on 1998 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic and Theoretical Elucidation of Structural Contributions to Reactivity in Binuclear Non heme Iron Enzymes written by Jennifer Kathleen Schwartz and published by . This book was released on 2008 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic Studies of Mixed valent Binuclear Non heme Iron Active Sites written by James Malcolm McCormick and published by . This book was released on 1991 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic and Theroretical Definition of Binuclear Non heme Iron Active Sites written by Yi-Shan Yang and published by . This book was released on 1999 with total page 558 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic and Theoretical Studies of Complexes which Model the Active Sites of Non heme Iron Proteins written by Carl A. Brown and published by . This book was released on 1994 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book X ray Absorption Spectroscopic Studies of Binuclear Non heme Iron Complexes and Their Dioxygen Adducts written by Heather Bufford and published by . This book was released on 1995 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic Characterization of Binuclear Non heme Iron and MN FE Active Sites written by Yeonju Kwak and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Binuclear non-heme iron enzymes catalyze various reactions including H-atom abstraction, desaturation, hydroxylation, and electrophilic aromatic substitution through O2 activation. In addition, they protect cells from oxidative stress and regulate iron levels in the cell. These enzymes utilize two irons and have common structural motif of 2-His / 4-carboxylate. Despite the enzymes' structural similarities, subtle changes at their active sites allow these enzymes to have different reactivities. Understanding the active site structures of these enzymes and the key mechanistic features related to these structures can provide a basis for potential applications: they could be drug inhibition targets to treat cancer, diabetes, and pathogenic diseases; they could work as biocatalysts; and they could carry out bioremediation reactions. In this dissertation, studies that examine three binuclear non-heme iron and Mn/Fe enzyme active sites (class Ic ribonucleotide reductase, ferritin variants, and bacterioferritin) and peroxo-bridged biferric model complexes are described. A combined spectroscopic methodology of nuclear resonance vibrational spectroscopy (NRVS), circular dichroism (CD), magnetic circular dichroism (MCD), and variable temperature, variable field (VTVH) MCD is used to probe geometric and electronic structures of Mn and Fe centers in protein active site and in model complexes.

Download or read book Spectroscopic and Structural Studeis sic of Core Variation in Binuclear Iron Families written by Pin-Pin Wei and published by . This book was released on 2006 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic and Theoretical Studies of Mononuclear Non heme Iron Enzymes written by Adrienne Renee Diebold and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mononuclear non-heme iron enzymes are an important class with a wide range of medical, pharmaceutical and environmental applications. Within this class, the oxygen activating enzymes use Fe(II) to activate O2 for reaction with the substrate. The focus of this thesis is on understanding two major themes of the oxygen activating enzymes - the role of the (2His/1 carboxylate) facial triad and the initial O2 reaction steps of alpha-keto acid-dependent dioxygenases - using a combination of spectroscopic techniques and DFT calculations. For ferrous systems, abs/CD/MCD/VTVH MCD studies define the geometric and electronic structure of the ferrous site. In combination with DFT calculations, a structure/function picture of the ferrous sites is developed. To extend these studies to the initial steps of O2 binding, studies with NO as an O2 analogue ({FeNO}7/{FeO2}8) utilize EPR/abs/CD/MCD/VTVH MCD spectroscopy with DFT calculations to elucidate important effects of the substrate on the {FeNO}7 bond. These effects are used in the computational extension to the experimentally inaccessible O2 bound complexes giving insight into the initial steps of O2 binding and activation. Taken together, these studies shed light on the rational for facial triad ligation at the Fe(II) site in the oxygen activating enzymes and how the Fe(II) ligand set tunes the specific reactivity of these enzymes.

Download or read book Binuclear Non heme Iron Complexes and Their Reactive Intermediates written by Anne Marie Spuches and published by . This book was released on 2003 with total page 876 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mononuclear Non heme Iron Dependent Enzymes Part B written by and published by Elsevier. This book was released on 2024-09-17 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mononuclear Non-heme Iron Dependent Enzymes, Volume 703 PART B focuses on methods for studying, characterizing, and leveraging the chemistry of mononuclear non-heme iron dependent enzymes. Chapters in this new release include Photoreduction for Rieske oxygenase chemistry, Insights into the Mechanisms of Rieske Oxygenases from Studying the Unproductive Activation of Dioxygen, Non-heme iron and 2-oxoglutarate enzymes catalyze cyclopropane and azacyclopropane formations, Obtaining precise metrics of substrate positioning in Fe(II)/2OG dependent enzymes using Hyperfine Sublevel Correlation Spectroscopy, Xe-pressurization studies for revealing substrate-entrance tunnels, and much more. Additional chapters cover A tale of two dehydrogenases involved in NADH recycling, Rieske oxygenases and/or their partner reductase proteins, Expression, assay and inhibition of 9-cis-epoxycarotenoid dioxygenase (NCED) from Solanum lycopersicum and Zea mays, Biocatalysis and non-heme iron enzymes, In vitro analysis of the three-component Rieske oxygenase cumene dioxygenase from Pseudomonas fluorescens IP01, Structure and function of carbazole 1,9a-dioxygenase, Characterization of a Mononuclear Nonheme Iron-dependent Mono-oxygenase OzmD in Oxazinomycin Biosynthesis, and much more. Provides detailed articles regarding how to study the structures and mechanisms of mononuclear non-heme iron dependent enzymes Guides readers on how to use partner proteins in non-heme iron enzyme catalysis Includes strategies to employ mononuclear non-heme iron enzymes in biocatalytic applications

Download or read book The Structure and Reactivity of Non heme Iron III Proteins and Model Complexes written by Bruce Prentiss Murch and published by . This book was released on 1987 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic and DFT Studies of Thiol and Olefin Coordinated Non heme Iron Dinitrosyl Complexes written by Miguel Angel Camacho Fernandez and published by . This book was released on 2010 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Recent developments involving the physiological implications of nitric oxide have spurred an intense interest in transition metal nitrosyl complexes, especially those that mimic the structures of biologically active metal nitrosyl complexes. In order to get insights on the electronic configuration, molecular orbital's interaction, and explain spectroscopic (NMR, EPR, and IR) observations, Density Functional Theory calculations were carried out on three series of metal nitrosyl complexes, Fe(NO)2 (P(OCH3)3)[eta]2-TCNE, [Fe2([mu]-RS)2(NO)4], and [Fe(NO)2(Im-H)]4 . The unusually high rotation barrier observed by NMR was explained through fragment analysis of Fe(NO)2 and TCNE. In addition, the difference of the g values between the reduced form of Roussin's red Esters and the typical dinitrosyl iron complexes is explained, for the first time, by of the difference in unpaired electron distributions between the two types of complexes, which provides the theoretical basis for the use of g value as a spectroscopic tool to differentiate these biologically active complexes.

Download or read book Bioinorganic Spectroscopy Structure function Correlations in Binuclear Non heme Iron Enzymes and Developing Nuclear Resonance Vibrational Spectroscopy for Characterization of Enzyme Intermediates written by Caleb Branson Bell and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The foci of this dissertation are: 1) combined use of spectroscopies for mechanistic understanding of the oxygen reactions of various non-heme iron enzymes and related model complexes, and 2) the development of the recently described nuclear vibrational resonance spectroscopy (NRVS) coupled with density functional calculations (DFT) for characterization of non-heme iron enzyme intermediates. Binuclear non-heme iron enzymes are involved in many medically and industrially important processes such as DNA synthesis by ribonucleotide reductase (RNR), conversion of methane to methanol by methane monooxygenase (MMO), fatty acid desaturation by [Delta]9 desaturase, iron storage and homeostasis by ferritins, degradation of aromatic compounds by various bacterial monooxygenases (ToMO, T4MO, etc.) and antibiotic biogenesis by p-aminobenzoate N-oxygenase (AurF), etc. Interestingly, these diverse reactions typically begin with O2 reacting with a biferrous active site, coordinated by highly conserved protein ligands (ExxH motifs) in four [Alpha]-helix bundles. Moreover, spectroscopically and chemically similar intermediates can be detected in many of the enzyme systems. The best studied in this family are RNRs, where biferric peroxo intermediates (P and P'), and the high-valent Fe(III)Fe(IV) intermediate X have been stabilized and spectroscopically characterized in wt and numerous variants. De novo designed four [Alpha]-helix bundles have been synthesized (the ~140 amino acid dui ferri (DF) peptide family) and are good models for binuclear non-heme iron enzymes. These systems provide a protein environment and can be viewed as a bridge between inorganic model complexes and native proteins. The pseudo-symmetric single chain version (DFsc) coordinates two ferrous ions by two His and four Glu amino acid residues. Circular dichroism (CD), magnetic CD (MCD) and variable-temperature variable-field MCD (VTVH MCD) show that this "active site" in DFsc has a 4-coordinate and 5-coordinate (4C+5C) geometry that is weakly antiferromagnetically coupled (J [approximately equal to] --2 cm-1) indicative of [Mu]1,3 carboxylate bridges, highly similar to RNR biferrous structures. Extended x-ray absorption fine structure (EXAFS) data are consistent with this assignment and show that one terminal carboxylate residue coordinates in a bidentate fashion. Changes in the CD/MCD/VTVH MCD and EXAFS spectra in the Y51L and E11D variants show that the 4C site is proximal to (but not bound by) Y51 and the bidentate carboxylate is coordinated to the 5C iron. Open coordination positions on both irons allow for dioxygen to react rapidly with the biferrous site. The reaction of biferrous DFsc with dioxygen yields a 520 nm ([Epsilon] = [weak approximation to]1200 M-1cm-1) species with a formation rate of 2 s-1, again similar to RNR (the Class Ia RNR from Escherichia coli has a dioxygen reaction rate of ~1 s-1, however the first species formed (intermediate P) has [Lambda]max = 700 nm). The resonance Raman (rR) spectrum obtained by excitation into the 520 nm feature in DFsc (and the E11D variant) proves this chromophore arises from a Tyr to ferric charge transfer (CT) transition. The 520 nm feature is lost by substitution of Y51 but not Y18, thus Y51 binds to the site after reaction with dioxygen. Subsequent binding of Y51 functions as an internal spectral probe of the dioxygen reaction and as a proton source that would promote loss of hydrogen peroxide. Coordination by a ligand that functions as a proton source could be a structural mechanism used by natural binuclear iron enzymes to drive their reactions past peroxo biferric level intermediates. RNR's can be divided into 3 major classes based on the radical generating machinery. Class I RNR's utilize a dimetal cofactor that reacts with dioxygen and can be subdivided into Classes Ia, Ib and Ic based on sequence homology and metal dependency. Class Ia enzymes are the best studied an present in higher organisms including human (host) while Class Ib enzymes are typically found in pathogens. CD, MCD and VTVH MCD data on biferrous loaded Class Ib RNR from Bacillus cereus allow assignment of the active site as 4C+5C in solution, resolving discrepancies from available crystal structures. Differences in the zero-field splitting parameters (D and E) and magnetic coupling extracted from fits to the VTVH MCD data can be ascribed to differences in the bridging carboxylate conformations. FeII loading, monitored by CD, shows cooperative binding with Kd 100 mM, significantly stronger that the metal binding in Class Ia. This provides the pathogen a competitive advantage relative to host in physiological, iron-limited environments Returning to Class Ia, the recently discovered intermediate P' notably lacks structural definition. This is mainly due to the lack of spectroscopic handles from which to obtain the needed experimental data. What is know, however, is that this species directly forms intermediate X and is directly derived from the well-defined intermediate P. Spectroscopically, P' has Mössbauer isomer shifts ([lowercase Delta] = 0.52 and 0.45 mm/s) that are significantly lower than the cis-[Mu]1,2 peroxo P ([lowercase Delta] = 0.63 mm/s) and lacks the ~700 nm peroxo to ferric CT suggesting some change in coordination mode or protonation may be involved in P -- P'. Comparisons of the reduced and oxidized crystal structures show differences in carboxylate coordination modes and water binding that must occur at some stage along the reaction coordinate. All of these potential structural perturbations were systematically incorporated into computational models of the intermediate site and correlated with experimental data using density functional theory (DFT). Two potential reaction pathways consistent with available experimental data were found. The first involves water addition to Fe1 of the cis-[Mu]-1,2 peroxo intermediate P causing opening of a bridging carboxylate to form intermediate P' which has an increased electron affinity and is activated for proton-coupled electron transfer to form the Fe(III)Fe(IV) intermediate X. While the second, more energetically favorable pathway, involves addition of a proton to a terminal carboxylate ligand in the site which increases the electron affinity and triggers electron transfer to form X. Vibrational characterization could, in principle, distinguish these pathways. However, the lack of a reasonably intense chromophore precludes rR experiments. The recently available method of nuclear vibrational resonance spectroscopy (NRVS) does not have these chromophoric constraints and can provide the needed vibrational data for P'--and many other "spectroscopically challenged" intermediates in non-heme iron biochemistry. The vibrations enhanced in NRVS are typically lower in energy and differ from those observed in rR, thus studies on well defined model complexes are needed prior to intermediate studies. A series of mononuclear Fe(IV)=O have been characterized by NRVS coupled with DFT calculations to define NRVS spectral assignments and set a foundation for vibrational characterization of non-heme iron enzyme intermediates. These studies show that the NRVS spectrum is rich in structural information. Of the four Fe(IV)=O models, supported by the 1, 4, 8, 11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMC); N, N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine (N4Py); N-benzyl-N, N', N'-tris(2-pyridylmethyl)-1,2-diaminoethane (BnTPEN); and 1,1,1-tris{2-[N(2)-(1,1,3,3-tetramethylguanidino)]ethyl}amine (TMG3tren) ligand sets, only the trigional bipyramidal geometry (relative to the 6C approximatly C4v geometry of TMC, N4Py and BnTPEN) enforced by the TMG3tren ligand affords a high-spin species. Isotope sensitive Fe-O stretches are observed for all complexes at 820 to 831 cm-1. However, at lower energy (

Download or read book Binuclear Non heme Iron Catalysts written by and published by . This book was released on 2004 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project involved the investigation of the ability of non-heme iron metalloenzyme reactivity model complexes to catalyze the oxidation of alkane and arene molecules. The objectives were to synthesize a series of non-heme mononuclear and dinuclear iron complexes, characterize their electronic structure and reactivity properties, characterize intermediates formed during oxygen atom transfer chemistry, and elucidate the mechanisms and specificity of the reactions.

Download or read book Structure function Correlations of Binuclear Non heme Iron Enzymes and Their de Novo Models written by Rae Ana Snyder and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Binuclear non-heme iron enzymes are pervasive in nature and catalyze a variety of biologically important reactions, including reactions relevant to the biosynthesis of DNA, fatty acid metabolism, the protection of pathogens from oxidative stress, cell signaling, iron storage, and many others. Elucidating the structures of their diiron active sites and the contributions of these structures to reactivity can provide molecular level insight into catalysis. The near IR circular dichroism (CD), magnetic circular dichroism (MCD), and variable temperature variable field (VTVH) MCD spectroscopies form a powerful methodology that allows for detailed structural understanding of the diiron active sites in these enzymes. Presented are studies that focus on myo-inositol oxygenase, an enzyme with significance to human health, and de novo designed diiron proteins that model native enzymes.